This application relates to an improved lid-type seal for cans and buckets, particularly large plastic cans and buckets.
Currently, paint buckets are generally made of steel. One reason for this is that it has not been previously possible to economically manufacture a large bucket made of plastic, which can be sealed with a paint can-type lid in which the lid firmly remains on the bucket until it is pried off. For example, paint buckets should be able to stand at least a four-foot drop on its mouth edge without losing the lid and spilling the paint.
The conventional configuration of a paint can seal, when molded in plastic, is generally inadequate for this rigorous requirement.
Accordingly, plastic paint buckets and other containers have been proposed in which a rubber sealing ring is provided to prevent leakage, but cost factors have made this arrangement relatively non-competitive.
In accordance with this invention, a seal structure between a plastic bucket and lid is provided which shows greatly improved resistance to opening by flexing wall action of the bucket mouth inwardly or outwardly, as would take place where a full paint bucket drops upon its rim. This is accomplished by providing, in addition to the usual rim seal in which the periphery of the lid grips from the outside an annular portion of the bucket rim, an added internal lid seal for gripping action internally of the annular portion of the bucket rim. Accordingly, this double seal holds even in the presence of substantial shock and flexing applied laterally to the bucket rim, but at the same time the lid can be peeled off with a screwdriver or the like in a manner analogous to the conventional opening of a paint bucket.
Also, radially positioned reinforcing ribs are provided for selective rigidity in the plastic bucket lid, which greatly improves the retentiveness of the lid under conditions of stress.
Heisler U.S. Pat. No. 3,817,420 discloses a bucket and lid connection arrangement having an internal seal, in which the bucket rim is a non-standard, double-walled structure. This exhibits significant disadvantage because of the need of the paint bucket industry for paint buckets of essentially conventional shape, capable of passing through the present filling machinery and the like.